Abstract

{mosimage}An excellent window of opportunity in the world blueberry market exists for the Australian blueberry industry, particularly in the earlier regions.

Marketing, however, must be backed up by the production of a quality fruit product, and this in turn must be established on some important horticultural foundations.

The choice of a suitable site involves finding suitable soils both structurally as far as aeration is concerned, and with a pH from 4.5 to 5.5 It also requires the choice of suitable varieties for the climatic conditions and adequate water.

The question of which variety to grow will be answered differently in different climatic zones and for differing potential uses. The proven highbush varieties for colder areas of Australia are Bluecrop and Brigitta, although there is a need to be assessing some of the new U.S. highbush releases.

In the warmer climate areas, the proven varieties at present are Sharpeblue and Misty (on some soils). Seedlings and new selections are being evaluated by private commercial companies in order to identify new selections with potential to provide high quality fruit early in the season, to target the October - November "window of opportunity".

Foundation No. 1. Site Choice 

Soils 

one of the things that struck me about the industry in the U.S. was the way in which the growers had developed "Mulching Mania". One grower in Florida had brought onto his property in excess of 200 semi-trailer loads of pine bark to build pine beds. The blueberries seem to do fine in these beds for a few years, but the issue that I raised with the growers was "Why are these pine beds working?" And behind my question of course was the thought that this was not an option to me because of the cost of pinebark and transport to our farm.

The key issues regarding the suitability of various soil types are as follows .....

1. SOIL pH. ......... blueberries are acid loving plants that do best in soils with a pH in the range from 4.5 to 5.5 although soils outside this range may be modified either with elemental sulphur (where the pH is too alkaline) or lime / dolomite (where the pH is too acid). It is important to remember that where soils are modified as such, deficiencies or toxicities of some elements may occur.
   
   
2. SOIL STRUCTURE / AERATION ...... I suspect that this may be the most important factor in the success of mulching with pine bark, as blueberries have a very fine fibrousy root system that needs a porous medium in which to grow, similar to the coarse sand in which they originated. Careful soil preperation, including the establishment of high mounds, and the use of weed matting or polyethylene strips to cover the mounds to prevent compaction of the soils underneath is very beneficial to the growth and establishment of a healthy root system.

Climate 

there are several issues involving the climatic suitability of an area, the most important of which are the availability of winter chilling, and the likelihood of frosts during the periods of flowering and fruiting.

A lack of chilling during the winter months may lead to problems of late leafing out and hence causing stress to the plant as it ripens the fruit without enough leaves carry it. Keeping the plant evergreen over the winter months using low levels of fertiliser, and hence keeping the mature leaves on the plant helps to overcome this problem in lower chilling areas, although not all low chill varieties will consistently evergreen as they mature.

Water

An adequate supply of water cannot always be assumed these days with restrictions on the issuing of new water licences in some states. A professional assessment of the availability of water, the quality of water and the design of an efficient means of applying the water to the plants is essential to the building of a firm foundation to the plantation.

Foundation No. 2. Which Variety ?

The choice of variety will vary according to the climatic zone in which the berries are to be grown and the prospective market into which they are being sold.

Highbush Varieties - the two most successful varieties of highbush blueberry being grown in the Southern states are without doubt the varieties Brigitta and Bluecrop. A brief description of these is as follows .....

BLUECROP: this is the most widely planted variety worldwide, setting the standard for other varieties. It is consistently high yielding, and withstands spring frosts quite well. It is a mid season variety, standing upright and vigorous, with large lightblue fruit. The bush is very productive and the fruit is flavourful and firm with a small scar. Bluecrop can be machine harvested successfully.

BRIGITTA: this is a late variety that was released from the Institute for Horticultural Development at Knoxfield in 1978. It is one of the highest quality berries available, with large light blue fruit that is firm and crisp. The fruit stores for long periods, keeping its quality very well. The bush is upright and vigorous. Brigitta is currently becoming very popular in the U.S., Canada, and Europe.

During my recent visit to highbush growing areas in the United States, I investigated the new releases of blueberries that show some potential for highbush growers in the Southern areas of Australia. The following varieties appeared to be the ones that would be most beneficial for growers to import through Quarantine and to trial.

I cannot stress enough how important that it is for the industry to be proactive with regard to obtaining the best germplasm available, and assessing it in various localities as quickly as possible. The following new varieties look good enough to me to commence commercial trial plots as soon as material becomes available.

DUKE: this appears to me to be the most outstanding release in the U.S. and it is being planted as fast as the propagators can produce it. This variety has demonstrated the potential to produce high yields of early fruit of high quality fruit. The berries are firm and medium blue, with a crisp flesh and maintain an even size throughout the season. The fruit is being machine harvested for the fresh fruit market. The bush is strong and productive with the fruit ripening 10 days before Bluecrop.

TORO: the fruit of Toro hangs in large clusters like grapes, and is consistently large with exceptional colour and flavour. It is a mid season variety that is produced on a spreading, stocky bush, producing consistently high yields.

LEGACY: this is a late season variety with the curious habit of maintaining evergreen leaves during the winter. The plants are vigorous and upright to 2 metres. It has a highly regarded berry flavour, and the berries are medium large and light blue. It is a heavy yielder and much appreciated by pickers.

Three varieties that originated in New Zealand have been imported into this country, and from observations of the three, the most likely prospect for commercial production here is the variety REKA.

REKA: this is a vigorous and upright variety that ripens between earliblue and Bluecrop. It is extremely productive producing medium blue fruit that is firm and with a small scar. It appears that Reka will tolerate a wide range of soils and wetter areas than most other varieties. It is becoming more popular with growers who are machine harvesting for the process fruit market.

Southern Highbush Varieties

There is a unique window of opportunity for the production and marketing of fruit during the months of October and November, a time when there are little or no fresh blueberries available anywhere else in the world. This potential was seen decades ago in the State of Florida in the United States where Prof. Ralph Sharpe saw the potential to produce blueberries in the month of April, prior to the fruit seasons in both Georgia and North Carolina.

The rabbiteye varieties at that time were too late in producing, ripening their fruit in the summer months during periods of high heat and humidity, due to the fact that they have a much longer period from bloom to ripen than the highbush types.

Prof. Sharpe made scores of crosses incorporating the genes of the low chill requiring lowbush, Vaccinium darrowi, and then backcrossing early flowering tetraploid selections to some of the northern highbush varieties. This work commenced in approximately 1954, and by the end of 1967 over 150,000 seedlings had been evaluated. The criteria for selection here were earliness in budbreak after a mild winter, Early fruit, good fruit size and flavour and healthy vigorous plants.

The first varieties to be released from this programme were Sharpeblue and Flordablue, which were released in 1976, followed by Avonblue in 1977. These varieties were imported into Australia in 1978 and released to the industry in 1980.

The variety Sharpeblue became the most important commercial variety in Australia by the mid 1980s.

Southern Highbush Variety Description

There has been a commercial interest in the assessment of new varieties of southern highbush blueberries in Australia by some Australian companies involving the importation of varieties from the United States, and the assessment of seedlings of various breeding lines from overseas breeding programmes. Those programmes have seen the assessment of many new selections from the programmes of Florida, Mississippi, Georgia and North Carolina, as well as the assessment of 40,000 seedlings locally. The long term view of those programmes is to eventually replace the standard low chilling highbush varieties that are currently being grown, with vigorous, high yielding selections producing early, high quality berries.

New varieties have been brought into Australia for assessment in these areas, but as yet have not been adequately assessed. These varieties include the USDA varieties released from Mississippi recently Biloxi, Magnolia, and Jubilee.

The varieties that have stood the test of time in Northern NSW are as follows:

SHARPEBLUE: this has proved to be the most vigorous and adaptive release. The bush is tough and vigorous, generally maintaining an evergreen appearance throughout the winter months. It has grown well in both sandy soils and heavier loams. The fruit has a pleasant flavour, is large and of medium blue appearance. The fruit has a wet scar, and is likely to become soft during very hot weather, meaning that it needs to be harvested frequently to overcome this.

MISTY: this variety is a true enigma, in that where it grows vigorously, such as on the red kraznozem soils of Northern NSW, it is very profitable and popular, yet on other soils it has often not grown well and is not a variety of popular choice. To produce high quality, early fruit, Misty is best grown under the evergreen system with attention being paid to nutrition and leaf diseases in order to keep the older leaves. It is an early fruiting variety, with light blue, medium to large fruit of excellent flavour.

GULF COAST: the variety Gulf Coast has produced good crops of fruit, with good vegetative bud break in some of the very low chilling localities where it has been trialled. The bush is vigorous and upright, with moderate toughness. The fruit is medium to large blue with a medium colour. The fruit has a problem in that it holds the stems on many of the berries at harvest. The flavour of the fruit is medium.

O'NEAL: this variety is an early erect bush that has a short "bloom to ripen" period, making it suitable in areas with late frosts. The berry has a distinct, very sweet flavour, and is appreciated on the fresh fruit market. I would estimate that it would be a good variety for planting on the cooler tablelands area.

Varieties and Markets

The choice of variety for a particular usage is very important prior to planting. It must be a very significant part of the overall strategy to be developed by the grower. This strategy ought to begin with the proper determination of market potential (eg. early fresh in northern areas, and late fresh / C.A. stored in the southern areas) and then the choice of varieties accordingly.

Where machine harvesting for fresh or processing is planned, then varieties that are suited need to be planted. In the case of properties where it is planned to market the fruit directly to the public through a U-pick operation, it may be that the varieties should be spread from very early to late, to maximise the time available to the public for visiting and harvesting. There appears to be a trend away from U-pick in the United States, possibly due to the fact that more women are working and they have less disposable time.

One area where there appears to be much interest in parts of America is that of the dried blueberry market. If this were to become a sought after commodity in Australia, it could lead to the development of blueberries in some of the dried fruits areas.